Perhaps not all of them, but that is how he felt.

[ And failure is something she can understand. It's something they could all understand. Those "heroes" that had survived the snapping of Thanos's fingers. What more could they have done or should they have done differently? In her case, she wished her sister had simply let her die. She wonders if the Soul Stone would never be obtained, but at least Gamora would have lived. ]

He was the one who failed to take the kill that would have prevented it.